www.pudn.com > audioProcessingtoolbox.rar > fftTwoSide.m

function [mag, phase, freq, powerDb]=fftTwoSide(signal, fs, plotOpt) 
% fftTwoSide: Two-sided FFT for real/complex signals 
%	Usage: [mag, phase, freq, powerDb]=fftTwoSide(signal, fs) 
 
%	Roger Jang, 20060411 
 
if nargin<1, selfdemo; return; end 
if nargin<2, fs=1; end 
if nargin<3, plotOpt=0; end 
 
N = length(signal);		% 點數 
freqStep = fs/N;		% 頻域的頻率的解析度 
time = (0:N-1)/fs;		% 時域的時間刻度 
z = fft(signal);		% Spectrum 
freq = freqStep*(-N/2:N/2-1);	% 頻域的頻率刻度 
z = fftshift(z);		% 將頻率軸的零點置中 
mag=abs(z);			% Magnitude 
phase=unwrap(angle(z));		% Phase 
powerDb=20*log(mag+eps);	% Power in db 
 
if plotOpt 
	% ====== Plot time-domain signals 
	subplot(3,1,1); 
	plot(time, signal, '.-'); 
	title(sprintf('Input signals (fs=%d)', fs)); 
	xlabel('Time (seconds)'); ylabel('Amplitude'); axis tight 
	% ====== Plot spectral power 
	subplot(3,1,2); 
	plot(freq, powerDb, '.-'); grid on 
	title('Power spectrum'); 
	xlabel('Frequency (Hz)'); ylabel('Power (db)'); axis tight 
	% ====== Plot phase 
	subplot(3,1,3); 
	plot(freq, phase, '.-'); grid on 
	title('Phase'); 
	xlabel('Frequency (Hz)'); ylabel('Phase (Radian)'); axis tight 
end 
 
% ====== Self demo 
function selfdemo 
[y, fs]=wavread('welcome.wav'); 
frameSize=512; 
startIndex=2047; 
signal=y(startIndex:startIndex+frameSize+1); 
signal=signal.*hamming(length(signal)); 
feval(mfilename, signal, fs, 1);